I visited the Grand-Hornu and Bois-du-Luc sites this Summer 2012. I think that the sum of these sites together was a wise choice for entry as a WHS. I wasn't very impressed by the Bois-du-Luc site. The main entrance gate is just about the best thing there is to see as the museum and the rest of the site is being refurbished now that it has been given the WHS status. The Grand-Hornu on the other hand was very well kept, very friendly and helpful staff welcome you and are willing to give you information. I was impressed by how big this site was and by the fact that so much attention was given to build this mining site. Once you go in this site, you would think it could be anything BUT a mining site!!! Really worth visiting Grand-Hornu and perhaps Bois du Cazier has much more to offer than the other 2 sites.